Conventionally, for instance, a general solenoid valve is composed as shown in FIG. 9.
That is, as shown in FIG. 9, a solenoid valve 100 is provided with a control unit 104 comprising a valve element 102.
Moreover, the control unit 104 of this solenoid valve 100 is provided with an electromagnetic coil 108 to which a driving portion 106 is passed through as shown in FIG. 9.
In addition, the electromagnetic coil 108 is provided with a bobbin 120 where the winding wire is rolled and as to surround the periphery of the bobbin 120, it is molded with a molding resin 112.
In addition, as shown in FIG. 9, the electromagnetic coil 108 is provided in a magnetic frame 114, and fixed to the driving portion 106 by the magnetic frame 114.
That is, the driving portion 106 is passed through to a driving portion inserting through hole 118 formed to the center section of a base plate portion 116 of the magnetic frame 114 and a driving portion inserting through hole 122 of the bobbin 120.
In addition, into a bolt inserting through hole 126 formed to the upper part of an attracting member 124 of the driving portion 106, a fastening bolt 132 is screwed together, through a bolt inserting through hole 130 formed to the center section of an upper plate portion 128 of the magnetic frame 114.
As a result, an electromagnetic coil 108 is passed through to the driving portion 106 and is fixed, so that a control unit 104 of the solenoid valve 100 is composed.
In addition, the driving portion 106 is provided with a plunger casing 134, and a plunger 136 in which the valve element 102 is fixed that can be moved upwardly and downwardly in this plunger casing 134.
In addition, between the attracting member 124 and the plunger 136, the plunger 136 is urged downwardly, that is, an urging spring 140 that urges the valve element 102 in the direction of the valve seat 138 is disposed.
As for such solenoid valve 100, by applying the electric current to the electromagnetic coil 108, the plunger 136 is moved in the directions of the attracting member 124 against the urging spring 140.
As a result, the valve element 102 connected with the plunger 136 is separated from the valve seat 138, so that a valve port 142 is opened.
Moreover, by interrupting the application of the electric current to the electromagnetic coil 108, the plunger 136 is moved in the direction that separates from the attracting member 124 by the urging force of the urging spring 140.
As a result, the valve element 102 connected with the plunger 136 is abutted to a valve seat 138, and the valve port 142 is closed.
Moreover, when the alternating current is applied to the electromagnetic coil 108, the magnetic flux is generated.
Consequently, the plunger 136 is moved in the direction of the attracting member 124 against the urging spring 140.
As a result, the state that the plunger 136 and the attracting member 124 are abutted, that is, the state that the valve element 102 is separated from the valve seat 138 and the valve port 142 is opened is maintained.
Conventionally, for the generation of the eddy current, in an annular groove 146 for the coil installation which is formed to a lower end surface 144 that faces to the plunger 136 of the attracting member 124, an annular shading off coil 148 (shading off ring) is installed.
In this case, the electromagnetic coil 108 which is used to drive the solenoid valve 100, power consumption is different in each power-supply voltage.
Therefore, it is necessary to prepare it by the winding specification such that the temperature rise tolerance limit of electromagnetic coil 108 is not exceeded.
In a word, the plunger 136 can not be attracted only by the generation of the alternating field in the electromagnetic coil 108.
Therefore, the structure that the plunger 136 is attracted upwardly in the direction of the attracting member 124 by embedding the shading off coil 148 in the attracting member 124 (or the plunger 136 side), so that the eddy current is generated, is adopted.